Apparatus and Method for Making and Assembling a Multi-Lens Optical Device

ABSTRACT

A system for aligning a plurality of high-precision lenses in a lens train. Each of the lenses has at least two alignment tabs disposed around the perimeter of the lens. The lenses are aligned by placing the lenses in a jig having a plurality of high-precision alignment blocks. The lenses are attached to a lower-precision shroud, having slots that receive the alignment tabs. A gap-filling adhesive is used to provide a high-precision fit for the lenses in the shroud.

STATEMENT OF GOVERNMENT INTEREST

The U.S. Government has a paid-up license in this invention and theright in limited circumstances to require the patent owner to licenseothers on reasonable terms as provided for by the terms of ContractNumber N00421-04-D-0010 awarded by the Naval Air Warfare Center AD(PAX).

BACKGROUND OF THE INVENTION

The present principles generally relate to optical systems, and moreparticularly, to a system and method for alignment of optical elementsin relation to each other in an optical device using references on theoptical elements.

Within the art of optical device design, multiple optical lenses arecommonly used together in a variety of optical devices. Multiple lenses(often referred to as a “lens train”) are commonly used in opticaldevices such as cameras, telephoto lenses, binoculars, telescopes,microscopes, night vision scopes, vehicular and marine periscopes, andthe like.

When fabricating optical devices with multiple lenses, the alignment ofeach individual lens relative to the other lenses in the lens train iscritical to achieving the desired optical performance. FIG. 1 aillustrates a pair of lenses 108, 110 in a lens train 100, in which thelenses 108, 110 are properly aligned with each other. A viewed object102 falls within the confines of a field of view 104. Light reflectingoff of the viewed object 102 passed through the first lens 108 and ismagnified to create an intermediate image (not shown). The intermediateimage is then focused onto a second lens 110 which performs additionalmagnification or other optical modification of the intermediate image,resulting in a final displayed image 112. When properly aligned, thefirst lens 108 focuses an image of the object 102 onto the second lens110 in a predictable and acceptable manner. Centerline 106 illustrates apath that may be ideal for referencing alignment of the first lens 108and the second lens 110. In contrast, FIG. 1 b illustrates the lenstrain 100 with the first lens 114 misaligned with respect to the secondlens 110. Accordingly, misaligned first lens 114 does not properly focusan intermediate image onto the second lens 110, resulting in anoff-center and/or distorted displayed image 116.

The current state of the art teaches methods for aligning lenses withrespect to other elements of an optical device using precision housingsand the like. In particular, with the rise of inexpensive digitalcameras, many manufacturers have attempted to align camera lenses withoptical sensors by providing a precision alignment surface within thehousing of the camera. Precision alignment of lenses in the currentstate of the art requires the lens housing to be manufactured to hightolerances in order to provide a high tolerance fit between the housingand the lenses. The necessity of providing precision lens housingsresults in an increased manufacturing cost.

SUMMARY OF THE INVENTION

In one respect, the invention comprises an optical device comprising alens train including a plurality of lenses, each of the plurality oflenses having a lens body and at least two lens tabs extending outwardlyfrom the lens body; and a housing having a plurality of lens tab slots,each of the plurality of lens tab slots being configured so that the oneof the plurality of lens tabs extends through the lens tab slot when thehousing and plurality of lenses are fully assembled.

In another respect, the invention comprises an apparatus comprising alens train including a plurality of lenses and a housing in which theplurality of lenses are contained, each of the plurality of lenseshaving a lens body and at least two lens tabs extending outwardly fromthe lens body, the shape and orientation of each of the at least twotabs on each of the plurality of lenses being different than the shapeand/or orientation of each of the at least two tabs on each of the otherlenses of the of the plurality of lenses.

In yet another respect, the invention comprises a method for aligning aplurality of lenses in a lens train to form an optical device, themethod comprising positioning each of the plurality of lenses on analignment jig at a first tolerance that is no less than a predeterminedalignment tolerance; affixing each of the plurality of lenses to ahousing at a second tolerance that is no less than the alignmenttolerance, the housing being manufactured to a tolerance that is largerthan the alignment tolerance; removing the plurality of lenses and thehousing from the alignment jig; and maintaining the relative position ofeach of the plurality of lenses within a third tolerance that is no lessthan the predetermined alignment tolerance after the plurality of lensesand the housing are removed from the alignment jig.

In yet another respect, the invention comprises a method comprisingpositioning a first lens in a first alignment block; affixing the firstlens to a housing while the lens is positioned in the first alignmentblock; and after the affixing step, removing the first lens from thefirst alignment block with the housing attached.

In yet another respect, the invention comprises a method of designingand making a first lens for use as part of an optical device having aplurality of lenses, the first lens including a lens body having atleast two optical surfaces and a perimeter edge located between the atleast two optical surfaces, the method comprising: forming at least twooptical surfaces of the lens body and a perimeter edge having a firstperimeter shape, the first perimeter shape being a simple closed curve;identifying a first portion of the lens body through which lightgenerated by the optical device could potentially pass when the opticaldevice is operated and a second portion of the lens through which lightgenerated by the optical device will not pass when the optical device isoperated; after the forming step, removing at least part of the secondportion of the lens body, the removing step resulting in the perimeteredge having a second perimeter shape that is a complex closed curve.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be described in conjunction withthe appended drawing figures, wherein like numerals denote likeelements. It should be understood that the drawings are for purposes ofillustrating the concepts of the present invention and are notnecessarily the only possible configuration for illustrating the presentinvention.

FIG. 1 a is a diagram illustrating an aligned lens train according tothe prior art;

FIG. 1 b is a diagram illustrating a misaligned lens train according tothe prior art;

FIG. 2 is a diagram illustrating a front view of one embodiment of alens having alignment tabs;

FIG. 3 is a right side view of the lens shown in FIG. 2;

FIG. 4 is a front perspective view of the lens shown in FIG. 2;

FIG. 5 is a rear perspective view of the lens shown in FIG. 2;

FIG. 6 is a front view of the lens shown in FIG. 2, including a dashedline showing a possible “rough-cut” perimeter shape;

FIG. 7 is rear perspective view of one embodiment of a alignment block;

FIG. 8 is a front perspective view of the alignment block shown in FIG.7;

FIG. 9 is a sectional view taken along line 9-9 of FIG. 7;

FIG. 10 is an enlarged partial view of area 10-10 of FIG. 9;

FIG. 11 is a sectional view taken along line 11-11 of FIG. 7, shown witha lens tab inserted in the alignment slot;

FIG. 12 is a sectional view taken along line 9-9 of FIG. 7, shown with alens tab inserted in the alignment slot;

FIG. 13 is a perspective view showing an alignment jig;

FIG. 14 shows the same view as FIG. 13, with several lenses and an imagesource assembly positioned on the alignment jig;

FIG. 15 shows the same view as FIG. 14, with an upper portion of thehousing positioned on the alignment jig;

FIG. 16 is a perspective view of a second embodiment of an alignmentblock positioned on a partial view of an alignment jig; and

FIG. 17 is an exploded view of the alignment block shown in FIG. 16.

DETAILED DESCRIPTION OF THE INVENTION

The ensuing detailed description provides preferred exemplaryembodiments only, and is not intended to limit the scope, applicability,or configuration of the invention. Rather, the ensuing detaileddescription of the preferred exemplary embodiments will provide thoseskilled in the art with an enabling description for implementing thepreferred exemplary embodiments of the invention. It being understoodthat various changes may be made in the function and arrangement ofelements without departing from the spirit and scope of the invention,as set forth in the appended claims.

To aid in describing the invention, directional terms are used in thespecification and claims to describe portions of the present invention(e.g., upper, lower, left, right, etc.). These directional definitionsare merely intended to assist in describing and claiming the inventionand are not intended to limit the invention in any way. In addition,reference numerals that are introduced in the specification inassociation with a drawing figure may be repeated in one or moresubsequent figures without additional description in the specificationin order to provide context for other features.

The present principles are directed to a system and method for alignmentof a series of lenses, called a lens train or an optical train. Inparticular, a lens train may be used to precisely set the magnificationand other advantageous properties of an optical device. It is to beunderstood that the present principles are described in terms of asystem for aligning optical lenses; however, the present principles aremuch broader and could potentially be used with other types of opticaldevices.

All examples and conditional language recited herein are intended to aidthe reader in understanding the present principles and the conceptscontributed by the inventor to furthering the art, and are to beconstrued as being without limitation to such specifically recitedexamples and conditions. Moreover, all statements herein recitingprinciples, aspects, and embodiments of the present principles, as wellas specific examples thereof, are intended to encompass both structuraland functional equivalents thereof. Additionally, such equivalents mayinclude both currently known equivalents as well as equivalents as yetundeveloped, including any elements developed in the future that performthe same function, regardless of structure.

Any reference to a lens, module, step or apparatus is intended toinclude both singular references and plural references, e.g., wherein areference to a lens may include multiple lenses mounted in a lenscarrier or holder, or multiple lenses molded together into a singleassembly or piece.

In the context of engineering tolerances in this application, a firsttolerance that is referred to as being “larger” than a second toleranceis intended to mean that the first tolerance is “looser” or less precisethat the second tolerance. For example, a tolerance of ±1.0 cm would belarger than a tolerance of ±0.1 cm.

Referring now to FIGS. 2 through 5, one embodiment of a lens 200 havinga lens body 204 and three alignment tabs 201, 202, 203 is depicted. Thelens 200 is preferably a unitary structure, precision-machined from asingle piece of material. The lens 200 is preferably made from anoptical-grade polymer, such as a cyclic olefin copolymer, for example.Alternatively, any material which is machineable to optical smoothnesscould be used.

As will be described in greater detail herein, one or more of the tabs201, 202, 203 is used to properly align the lens 200, first in analignment block and then in a shroud. The features and structure of thealignment block and shroud will be described herein.

In this embodiment, each tab 201, 202 and 203 extends outwardly from thelens body 204 and includes two faces and three edges. In the interest ofsimplicity, the faces and edges of tab 202 will be described in detailand it should be understood that tabs 201 and 203 havesimilarly-oriented faces and edges. Tab 202 includes opposing front andrear faces 220, 224, opposing side edges 221, 222 and an end edge 223.The front and rear faces 220, 224, and side edges 221, 222 and end edge223 are all preferably flat. As will be described in greater detailherein, any of the front and rear faces 220, 224, side edges 221, 222and end edge 223 may be used as a “control surface,” which is used toprecision-align the lens 200 during an assembly process. Each of thetabs 201, 202, 203 has a central axis 231, 232, 233, which bisects thewidth of each tab 201, 202, 203. For the purposes of this embodiment,the width dimension of each tab 201, 202, 203 is distance between theside edges.

In most embodiments, it is desirable to minimize the number of tab facesand edges that must engage bearing surfaces of the alignment blocks inorder to properly align the lens 200 in an alignment block. Properalignment of the lens 200 requires precision control of each of the sixdegrees of freedom, which comprise rotation and displacement relative tothe X-, Y- and Z-axes. Accordingly, in this embodiment, none of thecentral axes 231, 232, 233 of the tabs 201, 202, 203 are perpendicularto each other.

The lens body 204 (also referred to as the optical field) is the primaryactive optical region of the lens 200. The lens body 204 comprises afront face 212, a rear face 211 and a perimeter edge 213 that spans fromthe front face 212 to the rear face 211. The perimeter edge 213 willcomprise a surface in areas in which the front and rear faces 212, 211do not meet. The shape and contours of the front and rear faces 212, 211are dictated by the desired optical properties of the lens 200.

Notably, the perimeter edge 213 is irregular in shape in thisembodiment. This stands in contrast to most conventional optical lenses,which are manufactured with a relatively simple, regular perimeter shape(e.g., a circular, oval or elliptical shape). The irregular shape of theperimeter edge 213 is the result of additional lens material beingremoved in areas of the lens body 204 through which light is notintended to pass when the lens train is operated.

In order to determine where light will pass when the lens train isoperated, the lens train is computer-modeled, using an optics designpackage, such as Zemax® or CodeV® optical design software. As part ofthe modeling process, the path of light through the lens body 204 isdetermined. The lens train could be optimized to, among other variables,provide a low mass and maximum field of view.

Referring now to FIG. 6, the lens 200 is preferably manufactured inmultiple stages. First the lens body 204 is preferably “rough-shaped” toa perimeter shape 215 preferably comprising a simple, closed curve, suchas a circle or an ellipse. The front and rear faces 212, 211 are thencut to specification, which, in some applications, can include highlycomplex contours. After the front and rear faces 212, 211 are cut,portions of the lens body 204 through which light will not pass (asdetermined by the modeling process) are cut away, often leaving anirregular, complex perimeter shape (see perimeter edge 213). Lens tabs201, 202, 203 are cut during the machining of the perimeter edge 213.Cutting away unneeded lens material enables the lens train to be smallerand lighter, which is desirable in many applications, including mobiledevices and helmet mounted display systems, for example.

The lens manufacturing steps set forth in the previous paragraph couldbe carried out using a number of different manufacturing methods. Forexample, the “rough shaping” of the lens 200 could be performed by aninjection molding process and the cutting away of the portions of thelens body 204 through which light will not pass could be performed usinga precision machining process. Optionally, the front and rear faces 212,211 could also be “rough-shaped” by the molding process, then precisionmachined. In addition, the lens body could be injection molded into acircular shape, then rough cut to an elliptical shape, then cut to thefinal, irregular perimeter shape. Preferably, final machining isperformed using an ultra-precision diamond machining system.

FIGS. 7 through 10 show an alignment block 400 which, as will bedescribed in greater detail herein, is used to precision-position a lens(such as lens 200) during assembly of a lens train. The alignment block400 has a body 402 with an alignment slot 406 which is sized to receivea lens tab (such as tab 202 of lens 200). In order to aid in mountingthe alignment block 400 and to provide a more stable mounting surface,the alignment block may have flanges 401, 403 which extend laterallyfrom the lower end of the body 402. The alignment block 400 alsoincludes one or more pins or plungers 404, 405 for urging and holding aninserted lens tab against one or more of the surfaces of the slot 406.The plungers 404, 405 may be spring loaded (as shown in FIG. 10),threaded, or otherwise configured to force a lens tab into positionagainst one or more of the interior surfaces of the slot 406. Inalternate embodiments, other types of retaining devices, such as setscrews, for example, could be used instead of plungers 404, 405.

In this embodiment, the plunger 404 is positioned transverse to plunger405 and both are positioned at approximately the same vertical position.Accordingly, referring to FIGS. 11 and 12, plungers 404, 405 may be usedto press (urge) a face of a lens tab (for example, the face 220 of tab202) against a bearing surface 410 and position the end edge of the tab(for example, end edge 223 of tab 202) a desired distance from surface411. In other embodiments, variations in the number and/or position ofthe plungers 404, 405 are possible, depending upon the desiredpositioning characteristics of the lens that is to be positioned by theblock 400. In addition, a different surface could be used as the bearingsurface (i.e., the surface against which the lens tab is pressed) and/ormore than one surface of the alignment slot 406 could be used as abearing surface. It is, however, important that each pair of alignmentblocks engage the tabs of the lens retained by that pair of alignmentblocks in a manner that secures the lens in the proper position withrespect to all six degrees of freedom.

Referring to FIG. 13, a plurality of pairs of lens alignment blocks (forexample, blocks 400, 420) are shown arranged on a base 1002. The blocksand base 1002 collectively define an alignment jig 1000. Each alignmentblock is preferably rigidly affixed to the base 1002. Any suitable meanscould be used to affix the alignment blocks to the base 1002. Forexample, the alignment block flanges (such as flanges 401, 403) could bebolted, welded, bonded, or screwed, to the base 1002.

Various lens alignment block configurations may be used on the alignmentjig 1000 in order to accommodate the size, configuration and/or spacingof the elements in the lens train to be aligned. For example, a pair ofalignment blocks 421, 422, each having two slots, are used in jig 1000because of close spacing of two lenses 250, 251 (see FIG. 14). Skilledartisans will recognize that, while single and double slotted alignmentblocks have been illustrated, any number of slots may be employed on asingle alignment block.

Alignment blocks may also be provided to align elements of the lenstrain other than lenses. For example, alignment block 1004 is used toalign an image source assembly 1005 (see FIG. 14).

FIGS. 14 and 15 illustrate the assembly of an optical device 1100according to the principles of the present invention. Referring to FIG.14, a series of lenses, each having tabs formed thereon are positionedon alignment blocks. The process used to align each lens (lens 252, forexample) in its respective set of alignment blocks (alignment blocks400, 420, for example) is as described above in connection with FIGS.7-10.

In addition to dimensional tolerances, each optical component that formspart of the optical device 1100 will have a set of “alignmenttolerances,” which determine the amount of allowable error in therelative position of each of the optical components. Each set ofalignment tolerances may include translational alignment tolerances(i.e., allowable translational variation in the X, Y or Z axis) androtational alignment tolerances (i.e., allowable rotational variationabout the X, Y or Z axis). For example, the set of alignment tolerancesfor lens 252 define the maximum allowable variation from designspecifications in position of the lens in each of the six degrees offreedom. In this context, the “position” of lens 252 means its positionrelative to the other optical components of the device 1100. The valuesfor the set of alignment tolerances may vary among the opticalcomponents of a single optical device. Alternatively, a single set ofalignment tolerances may be applied to all of the optical components,with the tolerances being high enough to provide the desired opticalperformance of the device.

As discussed above, additional optical elements may be mounted in thejig 1000, and attached to the shroud. For example, FIG. 14 shows animage source 1005 mounted on alignment block 1004. Additionally, thebase 1002 of the jig 1000 may be recessed, or otherwise contoured, toaccept standard or frequently used elements.

It should be noted that the manner in which jig 1000 is used representsa departure from the prior art, in which adjustable alignment jigs andstandard or consistent lens registrations are used. In the presentinvention, a standard/consistent alignment block geometry is used andeach lens in the optical train is custom-cut to provide tab geometrythat will enable the lens to be properly positioned.

In this embodiment, the alignment tolerances of the lenses used inoptical device 1100 are preferably on the order of ±0.005 millimetersfor translation in the X, Y and Z axes and ±0.01 degrees for rotation inthe X, Y and Z axes. The dimensional tolerances for the shroud arepreferably on the order of ±0.13 millimeters.

Referring to FIG. 15, an upper portion 1102 of a shroud is properlyaligned and positioned atop the lenses using a finger plate 1006, whichis secured to a finger plate block 1007, using screws, bolts or anyother suitable fastener). The finger plate 1006 includes three fingers1008, 1009, 1010 which are attached to the upper portion 1102 of theshroud with screws or bolts (not visible in FIG. 15) which extendthrough threaded holes (also not visible in FIG. 15) in the upperportion 1102 of the shroud. The upper portion 1102 of the shroudincludes tab clearance slots. Some of the slots (such as slot 302) mateand cooperate with a corresponding slot in a lower portion of the shroud(not shown) to encircle a tab (e.g., tab 260). Other slots in the upperportion 1102, such as slot 303, completely encircle the tab (e.g., tab261) that extends through the slot.

As stated above, the use of a larger tolerance manufacturing method forthe shroud allows for a lower cost of manufacturing, as the shrouditself is generally not critical to the operation of the lens train. Itshould be understood that the relationship of the lenses to each other,and to any additional optical elements is critical to proper lens trainalignment. The shroud acts as a frame by which the lenses are maintainedin alignment. In order to maintain precision alignment of the lensesafter the lenses and upper portion 1102 of the shroud are removed fromthe jig 1000, any gaps between each of the clearance slots of the upperportion 1102 of the shroud and the tab that extends through eachrespective clearance slot are filled with a liquid adhesive prior toremoval from the jig 1000.

A thick, gap-filing cyanoacrylate glue is an example of a suitableliquid adhesive. There are a number of properties that are desirable ina preferred adhesive for this application, including (but not limitedto): a short cure time, water-resistance, post-curing expansion orshrinkage that is within the alignment tolerances for the opticalcomponents, a coefficient of thermal expansion that is within thealignment tolerances for the expected operating temperature range forthe optical device.

When the liquid adhesive has hardened sufficiently to prevent movementof the lenses, the finger plate 1006 is removed from the finger plateblock 1007 with the upper shroud 1102 and affixed lenses attached. Useof the liquid adhesive enables the position of each of the lensesrelative to the shroud to be maintained within its respective set ofalignment tolerances after being removed from the alignment blocks.

The lower portion of the shroud (not shown) is then secured to the upperportion 1102 and affixed lenses using any suitable method. For example,the finger plate 1106 could be flipped over and placed on a flatsurface. Then the lower portion of the shroud could be positioned atopthe upper portion 1102 and secured thereto using an adhesive. The lowerportion of the shroud provides some additional structural stability andcooperates with the upper portion 1102 of the shroud to encase thelenses and protect them from dust, moisture and other material thatcould be detrimental to the optical performance of the lenses.

The lens alignment and assembly method of the present inventionsimplifies shroud installation and reduces shroud manufacturing costs,because the lens tab alignment slots formed in the shroud can bemanufactured to a larger tolerance than the dimensional or alignmenttolerances of the lenses.

As a practical matter, in order to protect the lenses from dust,condensation and other material that could impair the optical propertiesof the lenses, a shroud is preferable in most optical applications. Itshould be noted that, in alternative embodiments, other types ofstructural members could be substituted for the shroud to maintain therelative alignment of the lenses after being removed from the alignmentjig 1000. For example, a structural member having openings therein couldbe used in an application in which the lenses will be contained inside alarger protective chamber. As used herein, the term “housing” isintended to refer to any rigid structural member (or multiple members)used to maintain the relative position of the lenses after being removedfrom an alignment jig and will remain part of the optical device afterit is fully assembled.

Another embodiment of the alignment block is shown in FIGS. 16 and 17and is generally referred to by reference numeral 500. In thisembodiment, the alignment block 500 is comprised of two portions 501,502, which form three slots 506, 507, 508 when joined. The slots 506,507, 508 perform the same lens tab alignment function as the slot 406 ofalignment block 400. The middle slot 507 is used with lenses having athird, downwardly-extending lens tab.

Each slot 506, 507, 508 includes a threaded opening 510, 511, 512(respectively) which accommodates a set screw (not shown) that is usedto hold a lens tab located in the slot against the portion 501 of thealignment block 500. Other types of devices, such as pins orspring-loaded plungers, could be used to hold the lens tabs in place.The middle slot 507 also includes a lateral opening 514, which is usedto hold a lens tab located in the middle slot 507 against a side wall515.

The two portions 501, 502 are bolted to each other using correspondingholes located in each of the two portions 501, 502 (e.g., holes 517,516). The alignment block 500 is preferably attached to a base 2002using holes located on the base 2002 and corresponding holes located inthe portion 502 of the alignment block 500. A pin (not shown) ispreferably inserted through the holes in the alignment block 500 and thebase 2002, then secured in position by a screw or bolt. Each pin ispreferably precision-machined to insure repeatable alignment between thealignment block 500 and the base 2002. The location of other alignmentblocks on the base 2002 is determined by the location of the mountingholes in the base 2002 for each block.

The two-piece construction of the alignment block 500 reduces thecomplexity and cost of adjustments to the lens alignment in block 500because such adjustments can be made by machining of only one portion501. In addition, small adjustments may be made to the spacing betweenthe two portions 501, 502 of the alignment block 500 by using shims (notshown). The use of shims allows for correction of any errors orinaccuracy in machining of the mating surfaces of the two portions 501,502 of the alignment block 500.

While the principles of the invention have been described above inconnection with preferred embodiments, it is to be clearly understoodthat this description is made only by way of example and not as alimitation of the scope of the invention.

1. An optical device comprising: a lens train including a plurality oflenses, each of the plurality of lenses having a lens body and at leasttwo lens tabs extending outwardly from the lens body; a housing having aplurality of lens tab slots, each of the plurality of lens tab slotsbeing configured so that the one of the plurality of lens tabs extendsthrough the lens tab slot when the housing and plurality of lenses arefully assembled.
 2. The optical device of claim 1, wherein each of theplurality of lenses has at least one translational alignment toleranceand each of the plurality of lens tab slots is manufactured to a firstdimensional tolerance, the first dimensional tolerance being larger thanthe at least one translational alignment tolerance.
 3. The opticaldevice of claim 1, wherein each of at least two lens tabs ismanufactured to a first dimensional tolerance and each of the pluralityof lens tab slots is manufactured to a second dimensional tolerance, thesecond dimensional tolerance being larger than the first dimensionaltolerance.
 4. The optical device of claim 1, wherein each of theplurality of lenses has a perimeter edge located between a front faceand a rear face and each of the plurality of lens tabs is located alongthe perimeter edge.
 5. The optical device of claim 1, wherein theposition of each of the plurality of lens tabs is fixed relative to arespective one of the plurality of lens slots by a gap-filing adhesive.6. An apparatus comprising: a lens train including a plurality of lensesand a housing in which the plurality of lenses are contained, each ofthe plurality of lenses having a lens body and at least two lens tabsextending outwardly from the lens body, the shape and orientation ofeach of the at least two tabs on each of the plurality of lenses beingdifferent than the shape and/or orientation of each of the at least twotabs on each of the other lenses of the plurality of lenses.
 7. Theapparatus of claim 6, wherein each of the plurality of lenses has aperimeter edge and the at least two tabs of each of the plurality oflenses are unequally spaced around the perimeter edge.
 8. The apparatusof claim 6, wherein the at least two tabs comprises three tabs.
 9. Amethod for aligning a plurality of lenses in a lens train to form anoptical device, the method comprising: positioning each of the pluralityof lenses on an alignment jig at a first tolerance that is no less thana predetermined alignment tolerance; affixing each of the plurality oflenses to a housing at a second tolerance that is no less than thealignment tolerance, the housing being manufactured to a tolerance thatis larger than the alignment tolerance; removing the plurality of lensesand the housing from the alignment jig; maintaining the relativeposition of each of the plurality of lenses within a third tolerancethat is no less than the predetermined alignment tolerance after theplurality of lenses and the housing are removed from the alignment jig.10. The method of claim 9, further comprising placing an upper portionof the housing into the alignment after the positioning step.
 11. Themethod of claim 9, wherein the affixing step further comprises using agap filling adhesive to adhere each of the plurality of lenses to thehousing.
 12. The method of claim 9, wherein the positioning stepcomprises inserting each of the at least two tabs located on each of theplurality of lenses into an alignment slot located in each of thealignment blocks.
 13. The method of claim 12, wherein the affixing stepfurther comprises using a gap filling adhesive to fix the position ofeach of the at least two tabs in a corresponding slot formed in thehousing to a tolerance that is no greater than the alignment tolerance.14. The method of claim 12, wherein the positioning step furthercomprises urging a control surface located on each of the at least twotabs of each of the plurality of lenses against a bearing surfacelocated in the alignment slot of each of the alignment blocks.
 15. Amethod comprising: positioning a first lens in a first alignment block;affixing the first lens to a housing while the lens is positioned in thefirst alignment block; and after the affixing step, removing the firstlens from the first alignment block with the housing attached.
 16. Themethod of claim 15, wherein the positioning step comprises urging acontrol surface located on each of a plurality of tabs located on thefirst lens against a bearing surface located on the alignment block. 17.The method of claim 15, wherein the positioning step further comprisespositioning a first lens in a first alignment block within a first setof alignment tolerances, the first set of alignment tolerances includinga tolerance for each of three degrees of translational freedom for thefirst lens.
 18. The method of claim 17, further comprising maintainingthe position of the first lens relative to the housing within the firstset of alignment tolerances after the removing step.
 19. The method ofclaim 18, wherein the affixing step comprises affixing the first lens toa housing while the lens is positioned in the first alignment block, thehousing being manufactured to a dimensional tolerance that is largerthan any of the tolerances of the first set of alignment tolerances. 20.The method of claim 18, wherein the positioning step further comprisespositioning a second lens in a second alignment block within a secondset of alignment tolerances, the second set of alignment tolerancesincluding a tolerance for each of three degrees of translational freedomfor the second lens.
 21. The method of claim 20, further comprisingmaintaining the position of the second lens relative to the housingwithin the second set of alignment tolerances after the removing step.22. A method of designing and making a first lens for use as part of anoptical device having a plurality of lenses, the first lens including alens body having at least two optical surfaces and a perimeter edgelocated between the at least two optical surfaces, the methodcomprising: forming at least two optical surfaces of the lens body and aperimeter edge having a first perimeter shape, the first perimeter shapebeing a simple closed curve; identifying a first portion of the lensbody through which light generated by the optical device couldpotentially pass when the optical device is operated and a secondportion of the lens through which light generated by the optical devicewill not pass when the optical device is operated; after the formingstep, removing at least part of the second portion of the lens body, theremoving step resulting in the perimeter edge having a second perimetershape that is a complex closed curve.
 23. The method of claim 22,wherein the identifying step further comprises creating a software-basedmodel of at least some of the optical properties of the optical device.24. The method of claim 22, wherein the forming step further comprisesforming at least two tabs that extend from the perimeter edge.
 25. Themethod of claim 22, wherein the forming step comprises forming at leasttwo optical surfaces of the lens body and a perimeter edge having afirst perimeter shape, the first perimeter shape being a circle or anellipse.
 26. The method of claim 22, wherein the forming step comprisesforming the at least two optical surfaces of the lens body and theperimeter edge having a first perimeter shape using an injection moldingprocess.
 27. The method of claim 22, wherein the removing step comprisesmachining at least part of the second portion of the lens body.